A. Obesity
It is estimated that there are over 300 million obese adult individuals worldwide. Obesity is defined as having a body weight that is 20 to 25 percent over the recommended body weight, taking into account a person's particular age, height, and sex. Usually, obesity results from eating too much and exercising too little—in other words, consuming more calories than one burns. Only a small percentage of obese individuals are obese due to a metabolic disorder.
Obesity affects virtually all age and socio-economic groups. Obesity has a multitude of physical and mental health consequences. Obese individuals are at increased risk for physical ailments such as high blood pressure, type 2 (non-insulin dependent) diabetes, coronary heart disease, osteoarthritis, gout, and certain types of cancer such as endometrial, prostate, colon and post-menopausal breast cancer. In addition to physical ailments, psychological disorders such as depression, low self-esteem, eating disorders, and distorted body image may occur in obese individuals.
The social consequences of being obese are significant. It is not uncommon for obese individuals to encounter discrimination in the job market, at school, and in social situations. Obesity can subject one to personal ridicule as well as limitations on recreational activities and clothing choices. From an increased risk of premature death to serious chronic conditions that reduce the overall quality of life, obesity is a major problem for those affected by it.
The common thread in obesity is that of a repeated imbalance in the amount of calories taken in versus the amount of energy expended. A small percentage of obese individuals ingest few calories yet maintain excess body mass because of low energy expenditure. However, more commonly, an obese person ingests a large amount of calories which sustain or increase body mass.
Why individuals overeat and become obese is a multi-faceted problem. The problem includes psychological, social, and physical components. A person may overeat in response to negative emotions such as boredom, sadness, or anger. Alternatively, a person may lack an understanding of the association between eating large quantities of energy-dense foods and weight gain and obesity. More commonly, individuals overeat in Western cultures due to hunger, social situations, and continuous access to food sources.
The term hunger describes a wide range of perceptions of an individual's drive to obtain and ingest food sources. The components of hunger include psychological drives such as eating for pleasure, and eating while socializing. The physical drives include low blood sugar, dehydration, or high levels of physical activity. The drive to overeat may be closely related to self-control issues; aberrant signals telling the individual to eat; lack of fully understanding the association between overeating and obesity; and many other possibilities.
The physical and psychological processes leading to hunger and eating are intimately intertwined. The stomach and duodenum, discussed further herein, communicate with the brain via nerve attachments as well as by hormones secreted into the bloodstream. Each structure facilitates the signals that may lead to the individual's perception of the need to eat. An example of this is “stomach growling,” which is a phase indicating that a certain amount of time has passed since the last meal. A person typically interprets this activity as hunger.
The opposite of hunger is satiety. Satiety is the feeling of abdominal fullness that occurs after eating a meal. A person is said to be sated if he or she feels fully satisfied after eating.
Because of the serious medical and social complications that result from obesity, a variety of treatments are commonly employed. Treatment methods are based on a variety of factors, such as the level of obesity, the person's overall health, and the person's motivation to loss weight.
Treatment may include diet modification, exercise, behavior modification, weight-loss drugs (e.g., dexfenfluramine, sibutramine, orlistat). In serve cases, where obesity threatens the individual's life, gastrointestinal surgery may be performed. Traditional surgical techniques typically focus on making the stomach pouch smaller, such as stomach stapling, gastric bypass, or implanting an inflatable band around the upper part of the stomach. Most commonly, a multi-faceted approached utilizing a combination of these factors is employed.
B. Gastroesophageal Reflux Disease
Gastrointestinal reflux disease (GERD) is an inflammation of the esophagus resulting from regurgitation of gastric contents into the esophagus. In symptomatic people, reflux is related to an incompetent lower esophageal sphincter (LES), which is a band of muscle fibers that closes off the esophagus from the stomach. Acidic or alkaline gastric contents return to the esophagus through the LES and causes symptoms.
GERD is believed to be caused by a combination of conditions that increase the presence of acid reflux in the esophagus. These conditions include transient LES relaxation, decreased LES resting tone, impaired esophageal clearance, delayed gastric emptying, decreased salivation, and impaired tissue resistance. Since the resting tone of the lower esophageal sphincter is maintained by both myogenic (muscular) and neurogenic (nerve) mechanisms, some believe that aberrant electrical signals in the lower esophageal sphincter or surrounding region of the stomach (called the cardia) can cause the sphincter to spontaneously relax.
The most common symptom of GERD is heartburn. Besides the discomfort of heartburn, reflux results in symptoms of esophageal inflammation, such as odynophagia (pain on swallowing) and dysphagia (difficult swallowing). The acid reflux may also cause pulmonary symptoms such as coughing, wheezing, asthma, aspiration pneumonia, and interstitial fibrosis; oral symptoms such as tooth enamel decay, gingivitis, halitosis, and waterbrash; throat symptoms such as a soreness, laryngitis, hoarseness, and a globus sensation; and earache.
Complications of GERD include esophageal erosion, esophageal ulcer, and esophageal stricture; replacement of normal esophageal epithelium with abnormal (Barrett's) epithelium; and pulmonary aspiration.
C. Barrett's Esophagus
Barrett's esophagus is a disorder in which the lining of the esophagus has cellular changes in response to irritation from gastroesophageal reflux (GERD). A small percentage of patient's with GERD develop Barrett's esophagus. The normal cells lining the esophagus, squamous cells, turn into an type of cell not usually found in humans, called specialized columner cells. The diagnosis of Barrett's esophagus is typically made by viewing the esophagus with an endoscope and obtaining a sample of esophagus tissue (esophagoscopy with biopsy).
Barrett's esophagus is believed to be caused by damage caused by GERD and/or biliary reflux, in which enzymes and bile are present in the stomach despite the control of acid. In some people, there is an abnormal bile flow backwards (refluxing) into the stomach. The reflux of the sticky bile causes the stomach to secrete copious amounts of acid in an attempt to neutralize the bile, which is alkaline. The excess acid causes bloating and increased pressure on the LES, which often results in GERD. Therefore, symptoms are similar to those of GERD and include heartburn and difficulty swallowing.
There is increasing evidence that reflux of bile plays a part in the pathogenesis of Barrett's esophagus. Bile injury to the gastric mucosa results in a “chemical” gastritis in which oedema and intestinal metaplasia are prominent.
Serious complications have been associated with Barrett's esophagus. These include an increased risk of esophageal dysplasia and esophageal cancer.
Traditional treatment includes general measures to control GERD, medications, and surgery previously described. In more serious cases, such as when biopsy indicates dysplasic cell changes associated with increased risk of cancer, surgical removal of a portion of the esophagus (resection of the esophagus) may be performed.